There's a big DVSA checkpoint area alongside the M74 motorway (Southbound) in the Beattock Summit area. Primarily used for checking HGVs. Car (and other type of vehicles) check points tend to be set up 'ad hoc', at more random locations, alongside 'A' roads, with ANPR systems likely being used to indicate which vehicles definitely need to be pulled over for further checking (no insurance, no MOT, no road tax, stolen vehicles, cloned vehicles and/or drugs or criminal activity markers, etc). And sometimes officers will pull over vehicles that just look plain unroadworthy.